You used to be able to place a handy Debugging Toolkit into the folder containing grimrock.exe and then access it in the console by typing dofile('debug.lua') (a list of commands was available within the file itself). However the dofile command is no longer available, likely to prevent arbitrary code execution from malicious mods.

Enabling Vsync may fix some issues, such as periodic freezing. This is because the game does not have a frame rate limiter, therefore it will tax the graphics card very heavily. Vsync forces a frame rate cap.

A known issue regarding certain graphics card drivers. Resetting the graphics driver to default values from the control panel can fix this issue. This issue, at least on AMD cards, seems to be caused by forcing anti-aliasing via the control panel. Disabling it should fix the issue. Morphological Filtering (MLAA) seems functional as an alternative, but it can make small text and objects blurry.